[2]Welcome to
this week's laboratory, "The Organization of Life: From Cells to
Organisms".Now you have finished
an introduction to chemistry and you are prepared to look at some higher levels
of biological organization.

[3]An
important property of life is that it is modular.This is the smallest unit of life, called the cell.The closed boundaries of a cell permit
concentrations and arrangements of chemical components that would be highly
improbable in a test tube.

[4]Large
organisms do not consist of a single large cell, but of many small ones.Molecules can only be efficiently moved
over very short distances.The
biochemical machinery in the cell must carry out thousands of chemical
reactions per second.If cells were too
large, they would not have adequate surface area for exchange of gases,
nutrients and waste products.The material
in the center of a large cell would either suffocate or starve itself.

[5] The cell has been called a miniature machine for
living--a chemical factory that takes both small and large molecules from the
environment and rearranges them into living matter.As you remember from Lab #1, cells are small, even though there
is quite a bit of size variation.A
period in your textbook is about 400 micrometers in diameter and most cells are
smaller than this.

[6]Now, turn
to your lab book and we will begin with an observation of some of the cells
nature has produced.Read the introduction
on page 4.2, and read over the definition of a cell on the next page. Then do
exercise 1 on pages 4.3 and 4.4.

[7]Now, I
would like you to check your sketch.You should have labeled the nucleus, the cytoplasm, and the outer
boundary--the cell wall.In all of the
advanced organisms the hereditary material, or DNA, is separated from the rest
of the cell by a membrane.The rest of
the material inside the cell is called the cytoplasm.Within the cytoplasm are a variety of smaller structures called organelles.

I B What is an Organelle?

[8]Here is a
view of the cell membrane which surrounds the cytoplasm.In Table 1 on page 4.6, I would like you to
write a very short summary of the function of each organelle.These are the most common organelles found
in plant and animal cells.Note that
the "cell membrane" is also called the "plasma
membrane".The function of the
cell membrane is to regulate the passage of materials into and out of the cell.

[9]You can
see in the diagram that the two main chemicals in the cell membrane are protein
and phospholipid.Pores allow for the
passage of the large molecules.Whether
or not a molecule is admitted to the cell depends on its size, shape,
electrical charge and chemical properties.To see the cell membrane in detail, we must use the electron microscope,
since the membrane is only about 70 angstroms thick.

[10]The
nucleus is the next organelle listed.The nucleus is the information center of the cell, storing genetic
messages.The nucleus contains the
nucleic acids DNA and RNA.

[11]ER or
endoplasmic reticulum is a system of double membranes in the cytoplasm which
serve as internal channels through which various materials can be transported.
The endoplasmic reticulum also functions to package various secretions by
surrounding them with a membrane.Let
me summarize the function of the endoplasmic reticulum: it serves to transport
and package materials.

[12]The
endoplasmic reticulum may also provide a structural framework for the
attachment of the ribosomes.In this
case it is called rough endoplasmic reticulum. The dots in this picture are
ribosomes which serve the function of synthesizing, or assembling,
proteins.The role of protein synthesis
is crucial to the cell, as you learned last week in chemistry.Endoplasmic reticulum without ribosomes is
called smooth endoplasmic reticulum.

[13]This
system of flattened membranes is called the Golgi complex.The Golgi complex may also be called the
Golgi apparatus or the Golgi body.It
functions to assemble and package secretions, such as digestive enzymes.

[14]Next, we
have lysosomes.Here you see lysosomes
labeled on the right edge of the picture. Can you find other lysosomes in the
picture?The function of the lysosome
is digestion. Cell organelles which are
worn out are digested and recycled in the lysosome.Lysosomes are found mainly in animal cells.Lysosomes contain hydrolytic enzymes, that
is, they catalyze the hydrolysis of large molecules into smaller ones.You can see in this picture some of the
other organelles we have discussed.The
cell membrane regulates the passage of materials and the nucleus is the control
center of the cell.The endoplasmic
reticulum transports and packages proteins and fat droplets store energy. Would this be a plant cell or an animal
cell?Animal is correct.Specifically, this cell is from the liver of
a rat.

[15]Here is a
plant cell.The dark ovals in this
electron micrograph are chloroplasts.The function of the chloroplast is to convert light energy to chemical
energy.The name for this process is
photosynthesis. The end product of photosynthesis is glucose, which you
constructed in laboratory 3.

[16]At the
center of the cell is a large space called a vacuole--an organelle common in
plant cells.The vacuole is surrounded
by a membrane and serves to hold fluid within the cell.This vacuole holds water, which saturates
the cytoplasm and gives the cell shape.Vacuoles are also found in animal cells.Vacuoles may serve a variety of functions.They can serve as a chamber for digestion,
storage or waste collection.Certain
molecules called pigments are sometimes stored in vacuoles, such as the red
pigment you find in roses, red onions, and beets.You can see small vacuoles near the edge of the cell.

[17]Also at
the edge of the cell, you will observe a structure labeled the cell wall.The cell wall gives support to plant
cells.A polysaccharide called
cellulose is the main structural material in plant cell walls.The cell wall is found only around the plant
cell--it is secreted from within the cell, but it actually lies outside of the
cell membrane.Animal cells have other
means of support, such as an internal or external skeleton, which maintains a
fairly constant shape for the animal.

[18]Here you
see a small but by no means insignificant organelle bounded by a double
membrane.This is a mitochondrion.The plural form of the word is mitochondria,
which you see in your lab guide.Mitochondria are known as the power plants of the cell.They carry out a complex set of chemical
reactions which produce the energy compound called ATP.ATP stands for adenosine triphosphate.But for now, simply make a note of the
capital letters ATP.The mitochondria
provides 90% of a cell's energy.Many
metabolic reactions take place here.Notice that the mitochondrion has internal membranes which are involved
in the chemical reactions of energy production.Mitochondria are more abundant in the cells that consume large
amounts of energy.They are also
situated near the structures within the cell which utilize the energy.For example, in muscle cells, the
mitochondria can be associated with the words metabolism, energy conversion,
and ATP.

[19]These are
ciliated cells which line the air passageways into our lungs.Dust and foreign matter are trapped in the
film of mucus secreted by goblet cells.The rhythmic beating of cilia sweeps mucus upward toward the throat.Cilia and flagella function in
movement.Write the term
"movement" after cilia and flagella.

[20]For some
cells, the whip-like action of cilia and flagella is the only means of
locomotion for the cell.In
multicellular organisms, the cilia may function to move a liquid past the
surface of the cell the way these ciliated cells of the trachea push mucus past
their cell surface.Ciliated cells also
circulate water through the gills of a clam and through the bodies of living
sponges.Ciliated cells also line our
nasal passages, carrying dust and mucus downward toward the throat.

[21]To
summarize, cilia and flagella function in movement...whether to propel cells
through water or to propel water past the surface of the cell. Remember
thatthese organelles are not just
isolated structures which work independently of each other in the cell. They
all function together as a working cellular unit.

[22]This is a
goblet cell, which secretes mucus.Mucus is a vital biochemical secretion. Beginning at number one in this
diagram, amino acids, sugars and sulfate are transported from the bloodstream
into the cell, and then they are packaged together at the Golgi complex.Note that the amino acids are first
assembled into protein at the ribosomes, numbers two and three.Packaging and transport takes place in the
Golgi complex at four, five and six, finally producing mucus in vacuoles at
number seven.Mucus is a complex
chemical, a combination of carbohydrate and protein--thus the name
glycoprotein.Finally, the mucus is
released, or secreted, at number eight.This is just one example of how organelles function together to perform
a specific task.

[23]Now I
would like you to try an easy question.

[24a]Following Table 1 in your lab book is exercise B-2"Organelles in Elodea".Elodea is a common freshwater plant you may
have seen in an aquarium.The common
name is also elodea.You may now follow
the directions for exercise two.

[24b]Be sure
to save your slide.We will use Elodea
for a demonstration of diffusion and osmosis.

I C Diffusion and Osmosis

[25]Now look
at part C on page 4.7 - "How do small particles disperse and gain entrance
to cells?" You may know this answer already.Small particles, like minerals and ions, enter cells by the
process of diffusion. The definition of diffusion is: "the random movement
of particles from a region of high concentration to a region of low
concentration."

[26]This
diagram is an example of diffusion.Diffusion occurs every time you add sugar or cream to coffee, or when
you wear a perfume or cologne.

[27]Osmosis
is "the diffusion of water through a semipermeable membrane."As with diffusion, osmosis will occur if
there is a higher concentration of water on one side of the membrane than on
the other.

[28]Here, the
tiny particles represent water molecules which are able to diffuse through the
pores in the cell membrane.Now read
the next section in your lab book:"How is a cell affected by its environment?"

[29]Here you
see the effect of putting a cell--in this case a sack with a semipermeable
membrane--into a hypertonic solution.Fill in Table 2 accordingly. The solute is the material that has been
dissolved in the water.In this case
the solute is sucrose, or table sugar.Next to the term "hypertonic", you should indicate that the
water concentration compared to the cell would be lower in the hypertonic
solution--that is, 90% as compared to 98%.Note that water diffuses out of the sack when it is put in the
hypertonic environment.You should also
indicate that the solute concentration in the hypertonic solution is higher
when compared to the cell.In this
example, it is 10% sucrose, compared to 2% sucrose in the cell.

[30]Here you
see an isotonic solution on the right, because it is the same as the cell:98% water.The solution on the left is hypotonic because it is 100% water.Now, fill in the table again for the
isotonic solution on the right and the hypotonic solution on the left. Now,
next to the word "isotonic", you should have the water concentration
and the solute concentration the same as that within the cell.For the hypotonic solution, you should have
noted that the water concentration is higher than in the cell and the solute
concentration is lower.Note that the
water concentration does not have to be 100%, but 100% is the most hypotonic solution
possible, such as rainwater or distilled water.The arrows emphasize that in the hypotonic environment, water
diffuses into the sack, and in the isotonic environment, there is no net change
in water movement. Complete the rest of this page and then complete"Elodea in a different
environment".Follow the steps and
obtain the instructor's initials.

[31]Your
sketch should indicate that the cell contents, or cytoplasm, have shrunk to
some extent and pulled away from the cell wall--similar to the diagram shown
here.Specific cells are adapted to
specific environments.The normal
environment for Elodea cells is hypotonic, such as a freshwater pond.The environment of organisms in the ocean or
in saltwater lakes is hypertonic.The
cells which live in your bloodstream require an isotonic environment.

[32]A picture
taken with a scanning electron microscope will give a somewhat 3-dimensional
view such as this.The shape of the red
blood cell is described as a biconcave disk, which gives it a high
surface-to-volume ratio.This allows
for rapid and efficient diffusion of oxygen molecules through the cell
membrane.

IITissues

[33]We group
similar cells together into units we call tissues.Read over the definition of a tissue in your lab guide. These
cells are a sample of human muscle tissue.The protein molecules in skeletal muscle are organized into very regular
patterns, thus we see dark bands as striations.All of these cells are similar, and they function together to
contract a muscle which moves the skeleton.

[34] Nerve tissue is found in the brain, spinal
column, and the nerves of higher animals, such as most of us humans.This is an individual nerve cell, or
neuron.The dark spots are the
connections or synapses with other nerve cells.

[35]The
structure of epithelial tissue is such that the cells are closely spaced and
are arranged in thin layers or sheets.Epithelial tissues make up the covering of the body, which is called the
epidermis or skin.Epithelial tissue
also lines the internal cavities and ducts, forming glands.

[36]In
exercise B-1 you will observe some of your own human epithelial tissue.You will observe cells like these called
squamous epithelium, which consists of thin, flattened cells arranged in one or
several stratified layers.

[37]You will
obtain epithelial cells in this manner.Be gentle when you scrape your cheek--you will not see any cells on your
toothpick with your naked eye, but they will be there nonetheless.Now follow the steps for Human Epithelial
Tissue under Roman numeral II.

[38]Connective tissue includes a variety of cell types. Dense connective
tissue forms tendons and ligaments. Cartilage, bone tissue, and blood, or
vascular tissue are consideredto be
connective tissues. The white blood cells in this picture are marked with an
"ly" for lymphocyte."Er" is for erythrocyte, or red blood cell, and "pl"
is for the platelets--involved in the clotting mechanism.Unlike epithelial cells, the cells of
connective tissue are scattered through an extensive extracellular matrix.

[39]Macrophages and white blood cells called lymphocytes are housed in
filters in the body called lymph nodes, which you see here."Ly" stands for lymphocyte, "ma"
is for macrophage.These are cells
which engulf invaders and clean up debris in the body tissues.They engulf particles by a process called
phagocytosis.

[40]This
depicts the process of phagocytosis.The cell forms a vacuole around the food particle.Later in this lab you will observe an organism
which looks very closely related to our white blood cells.You may even be able to observe the process
of phagocytosis.

III Organs

[41]Here you
can see a variety of organs which belong to our distinctive animal friend, the
frog.The organs of the frog are very
similar to the organs of the human.Thus when you study the frog, you are also studying yourself.Some organs in the frog and the human are
composed mainly of one type of cell.For example, the brain is made up of neurons and muscles are made up of
muscle cells.Other organs, such as the
small intestine, are a composite of different types of tissues.

[42]Here is
an electron micrograph of a cross-section of small intestine.The projections into the opening, or lumen,
of the small intestine are called villi.On the surface of each epithelial cell are tiny extensions of the cell
membrane called microvilli.

[43]Together,
these two types of projections produce a tremendous surface area for the small
intestine.It is in the small intestine
that digestion and absorption of most nutrients occur.Do exercise A-1 on pages 4.10 and 4.11.

[44]Look at
your answer to the question in step "e". Besure to locate the epithelial cells because of their vital
importance in the absorption of digested food in the form of simple
molecules.The size of the epithelial
layer is generally from 30 to 70 micrometers in thickness.Your answer should be in this general range.
Now turn to the top of page 4.12.

[45]This is
the small intestine again, and these projections, called villi, function to
increase the surface area of the small intestine for the absorption of
food.Write the function next to the
word "villi" at the top of the page.Again, the villi increase surface area for absorption.

[46]The
microvilli are microscopic projections on each epithelial cell in the small
intestine.Their function is the same
as that of the villi.In fact, the
entire surface area in the human small intestine is equal to 300 square
yards.This is enough surface area to
cover the floor of a 2700 square foot house.This would be a cheap floor covering--but it would be extremely
thin...The function of the epithelial
tissue is for the absorption of nutrients into the bloodstream.

[47]The
muscle tissue provides waves of contraction, called peristaltic waves.This constantly moves more nutrients past
the cells which do the absorbing.

[48]Connective tissue like this binds other tissues together.In the small intestine, it binds the muscle
cells to the epithelial cells.This is
a sketch of loose connective tissue, which provides a framework for every organ
in the body.

[49]The
nervous tissue was not visible in your microscope section.Nerve tissue provides stimuli to control the
muscle cell contractions.

V Organ Systems

[50]Read the
definition of an organ system in Roman Numeral IV.

[51]The organ
system you will now observe is the digestive system.We will examine the organs which work together to accomplish
digestion.Your frog is a fine example
of organization and adaptation.

[52]There are
steel probes on the demonstration table, so you don't have to use your
fingers.Find the tongue and see if you
can notice anything unusual about it.

[53]You might
have noticed that the tongue is attached at the front of the mouth.Why?If we could observe a living frog catch an insect, the tongue would
unroll.Of course, the living tongue
was more elastic.Run your dissecting
probe around the edge of the mouth to detect the tiny row of maxillary teeth,
which, along with the two vomerine teeth, help to keep the prey in the
mouth.In Table 4, the function of the
tongue is to taste and manipulate food.The frog's tongue also is used to catch its food.

[54]The food
passes through the esophagus to the stomach.Only the beginning and the end of the esophagus will be visible to
you.The esophagus functions to pass
the food from the mouth to the stomach.

[55]The
function of the stomach is to begin the digestive process.With the action of acid and enzymes and a
churning motion, the solid food is converted into a semi-liquid blob.The stomach of your frog has been cut open,
and you can look in to verify the fact that the frog swallows its food whole.

[56]Follow
the stomach downward and you will find a narrow constriction between the
stomach and the small intestine called the pyloric sphincter.The pyloric sphincter regulates the movement
of food from the stomach into the small intestine.The small intestine completes the digestive process.It is here that the food is completely
digested into molecules and absorbed into the blood stream. The small intestine
will eventually run into an enlarged portion.This is the large intestine.

[57]The
function of the large intestine is to absorb water from the digested mass of
food.The large intestine also absorbs
minerals, such as sodium, and vitamins which are manufactured by the bacteria
which live there.

[58]Remember
the process of osmosis?A great deal of
osmosis takes place between the body fluids and the small intestine.The water moves by osmosis from the body
fluids into the small intestine. Eventually this water must be reabsorbed into
the body to prevent dehydration.The
large intestine reabsorbs water--a homeostatic function that maintains water
balance in the animal.

[59]The liver
is easy to find.It is dark brown and
has three lobes.The liver produces a
liquid called bile that helps to digest fat by breaking it into tiny droplets.
Remember the emulsified fat in milk in lab 3. The liver is a metabolic factory,
doing an amazing variety of jobs including hormone and glucose regulation,
detoxification of poisons, removing nitrogen from amino acids, and storing
vitamins.

[60]The next
organ is the gall bladder.The gall
bladder stores the liver bile until it is emptied into the small
intestine.Look under the lobes of the
liver and you will find a small greenish or clear sack.This is the gall bladder.

[61]The next
organ, the pancreas, is a thin, light-colored organ located between the lower
end of the stomach and the first loop of the small intestine.The pancreas produces digestive
enzymes.Humans produce more kinds of
enzymes than a frog does.Why is
that?We have to be able to chemically
process a number of different kinds of foods.

[62]The next
item on your list is the fat bodies.The fat bodies are long, yellow structures, located under the digestive
organs.Fat is the most efficient way
to store energy--and that is the function of fat bodies.

[63]Finally,
the mesenteries are the connective tissue membranes which hold the small
intestines and the pancreas in place.We have seen microscopic views of connective tissue-- this will give you
a chance to observe the overall appearance of this tissue type.

[64]Now
answer this practice question.

[65]Now I
would like you to do exercise number three at the top of page 4.14

[66]Now we
will do exercise number four, and look at some other organ systems.The main organ of the circulatory system is
of course, the heart, which functions as a pump.The heart is a firm muscular organ, located right under the
liver.

[67]The
spleen is a dark, round sack located in the mesenteries of the small
intestine.Its function is to process
red blood cells, and to serve as a reservoir of red cells for emergencies.The white organ next to this spleen is one
of the testes.

[68]By moving
the heart gently to the right and then to the left you will expose the lungs,
the major organs of the respiratory system.The lungs may be prominent, or they may appear like this, as thin,
flattened sacks.

[69] The urinary bladder, which has probably collapsed
in your frog, and will appear as a thin sheet of connective tissue.The bladder and kidneys are important organs
of the excretory system.Gently push
the digestive organs to one side and you will find two flat kidneys lying
against the body wall.

[70]Notice
that the kidneys are covered by a membrane called the peritoneum.At the anterior or front end of each kidney
may be found the long, yellowish fat bodies.On the midline of each kidney should be a yellowish band of tissue
called the adrenal gland.This is an
endocrine gland that secretes hormones.

[71]If your
frog is a male, you will be able to find one of the small oval, whitish testes
at the anterior or front end of each kidney.

[72]If your
frog is a female, you will see an obvious, white mass of coiled oviducts and
you may find a mass of dark eggs.When
the eggs mature, they pass through the oviducts and are coated with several
layers of jellylike material. Now you may return your frog to the demonstration
table.

V Organisms

[73]Now we
are on Roman Numeral V, the last stretch of laboratory four.The organism is an easy level of
organization to comprehend.

[74]Here is
another organism,

[75]and
another.

[76]You have
looked at the frog, a multicellular, but dead, organism.How about a unicellular, but live one?

[77]This is
one of the neatest, the amoeba--an organism that consists of only one large
cell.Its unique motion consists of
extending lobe-shaped projections called pseudopods and having the cytoplasm of
the cell flow into them. White blood cells, such as lymphocytes, use amoeboid
movement and phagocytosis to capture infectious microorganisms in the blood.

[78]Here you
see a large amoeba capturing a paramecium.If you recall, this event is called phagocytosis.You may be able to observe this event in the
pond water sample we have provided.

[79]Now
complete the last page of laboratory four. Please be sure your microscope and
lab space is in order. Thank you.